1. Field of the Invention
This invention relates to a vibratory parts-feeder, and more particularly to a vibratory parts-feeder in which a bowl is torsionally vibrated.
2. Description of the Prior Art
The vibratory parts-feeder is widely used for handling different parts. FIG. 1 shows one example of prior art vibratory parts-feeders. It is denoted generally by a reference letter P. A cylindrical bowl B is combined with a base block R by plural sets of piled leaf springs Q. The plural sets of the piled leaf springs Q are obliquely arranged at regular angular intervals of 90 degrees in this prior art arrangement. The upper ends of the piled leaf springs Q are fixed to the bowl B by bolts b and the lower ends of the piled leaf springs Q are fixed to the base block R by the bolts b. An electro-magnet E on which a coil is wound, is fixed to the base block R. It is facing toward a movable core M fixed to the bowl B, and spaced by air gap S. The entire vibratory parts-feeder P is supported on the ground by vibration absorbing rubbers G.
When the coil is energized by an alternating current, the alternating vibratory force is generated to torsionally vibrate the bowl B. A not-shown spiral track is formed in the bowl B. Parts such as transistors, bolts and nuts are transported along the spiral track with the torsional vibration of the bowl B.
As shown in FIG. 2, each set of the piled leaf springs Q consists of three leaf springs a, b and c, contacted onto the slant Ba formed in the bottom portion of the bowl B. For the facilitation of the drawing, the three piled leaf springs a, b and c are exemplified. However, the number of the piled leaf springs is larger in the usual vibratory parts-feeder. Spacers d and e are interposed between the leaf springs a and b, and b and c. A contact plate f is contacted onto the front most leaf spring c. A bolt g is inserted through openings of the leaf springs a, b and c, spacers d and e and contact plate f into a threaded hole Bb of the bowl B. The bowl B is torsionally vibrated by vibratory force having a frequency near to a resonant frequency of the vibratory parts-feeder P. The resonant frequency is predetermined by a mass of movable parts including the bowl B and a total spring constant of the piled leaf springs Q. Usually, in order to obtain a resonant frequency near to the frequency of the vibratory force, the number of the leaf springs and the thickness of each leaf spring are adjusted or changed. As shown in FIG. 3, when the bowl B is torsionally vibrated, the piled leaf springs Q are twisted, and the node of the twisting is formed between the upper and lower ends of the piled leaf springs Q. The position of the node is determined by mass-ratio of the bowl B to the base block R. A large concentrated stress is imparted to the upper and lower ends of the leaf springs a, b and c. Accordingly, the leaf springs a, b and c are apt to be broken or damaged there. When the leaf springs a, b and c are broken or damaged, the piled leaf springs Q should be demounted and new leaf springs substituted. Such demounting and mounting operations of the piled leaf springs are troublesome and require much labor time.
On the other hand, this Assignee disclosed a control apparatus for a linear electromagnetic feeder in the Japanese publication number 7083/1987. The linear electromagnetic vibratory feeder controlled by the disclosed control apparatus is shown in FIG. 4. It is generally denoted by a reference letter F. A straight trough T, which is suspended from a stationary by coil springs q, is driven by a drive part D. It includes an electromagnet Y, piled leaf springs W and a drive transmitting portion N connected to a central portion of the piled leaf springs W. The piled leaf springs W are alternately bent with alternating vibratory force. The trough T is linearly vibrated through the transmitting portion N. Spacer plates are interposed between the leaf springs at both end portions. The piled leaf springs W are apt to be broken or damaged there. The mounting and demounting operations for substituting new leaf springs are troublesome and require much labor time.